DESCRIPTION
The LTC®3728L/LTC3728LX are dual high performance step-down switching regulator controllers that drive all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phaselockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase.

FEATURES
■ Dual, 180° Phased Controllers Reduce Required
   Input Capacitance and Power Supply Induced Noise
■ OPTI-LOOP® Compensation Minimizes COUT
■ ±1% Output Voltage Accuracy (LTC3728LC)
■ Power Good Output Voltage Indicator
■ Phase-Lockable Fixed Frequency 250kHz to 550kHz
■ Dual N-Channel MOSFET Synchronous Drive
■ Wide VIN Range: 4.5V to 28V Operation
■ Very Low Dropout Operation: 99% Duty Cycle
■ Adjustable Soft-Start Current Ramping
■ Foldback Output Current Limiting
■ Latched Short-Circuit Shutdown with Defeat Option
■ Output Overvoltage Protection
■ Low Shutdown IQ: 20µA
■ 5V and 3.3V Standby Regulators
■ 3 Selectable Operating Modes: Constant Frequency,
   Burst Mode® Operation and PWM
■ 5mm × 5mm QFN and 28-Lead Narrow SSOP
   Packages

APPLICATIONS
■ Notebook and Palmtop Computers
■ Telecom Systems
■ Portable Instruments
■ Battery-Operated Digital Devices
■ DC Power Distribution Systems